diff --git a/bootstrap.conf b/bootstrap.conf
index 7451d90..eb3a373 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -1,4 +1,4 @@
-# bootstrap.conf (Recode) version 2021-06-02
+# bootstrap.conf (Recode) version 2022-01-21
 
 # This file is part of Recode.
 #
@@ -66,7 +66,6 @@ gnulib_modules='
         pipe-posix
         quotearg
         sigaction
-        snippet/unused-parameter
         strndup
         sys_wait
         unistd
diff --git a/src/african.c b/src/african.c
index ce28eea..0fa5b39 100644
--- a/src/african.c
+++ b/src/african.c
@@ -122,6 +122,6 @@ module_african (RECODE_OUTER outer)
 }
 
 void
-delmodule_african (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_african (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/afrtran.c b/src/afrtran.c
index 8011a60..15a039f 100644
--- a/src/afrtran.c
+++ b/src/afrtran.c
@@ -334,6 +334,6 @@ module_afrtran (RECODE_OUTER outer)
 }
 
 void
-delmodule_afrtran (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_afrtran (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/atarist.c b/src/atarist.c
index 3097420..fd55c36 100644
--- a/src/atarist.c
+++ b/src/atarist.c
@@ -102,6 +102,6 @@ module_atarist (RECODE_OUTER outer)
 }
 
 void
-delmodule_atarist (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_atarist (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/bangbang.c b/src/bangbang.c
index 0ae9f9c..ab3e6ab 100644
--- a/src/bangbang.c
+++ b/src/bangbang.c
@@ -285,7 +285,7 @@ static const char *const translation_table[256] =
 
 static bool
 init_latin1_bangbang (RECODE_STEP step,
-		      RECODE_CONST_REQUEST request _GL_UNUSED_PARAMETER,
+		      RECODE_CONST_REQUEST request _GL_ATTRIBUTE_MAYBE_UNUSED,
 		      RECODE_CONST_OPTION_LIST before_options,
 		      RECODE_CONST_OPTION_LIST after_options)
 {
@@ -393,6 +393,6 @@ module_bangbang (RECODE_OUTER outer)
 }
 
 void
-delmodule_bangbang (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_bangbang (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/base64.c b/src/base64.c
index 3d20713..de4ab5c 100644
--- a/src/base64.c
+++ b/src/base64.c
@@ -261,6 +261,6 @@ module_base64 (RECODE_OUTER outer)
 }
 
 void
-delmodule_base64 (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_base64 (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/cdcnos.c b/src/cdcnos.c
index 5a9e04c..1afd053 100644
--- a/src/cdcnos.c
+++ b/src/cdcnos.c
@@ -339,6 +339,6 @@ module_cdcnos (RECODE_OUTER outer)
 }
 
 void
-delmodule_cdcnos (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_cdcnos (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/combine.c b/src/combine.c
index 54d5a94..91e1229 100644
--- a/src/combine.c
+++ b/src/combine.c
@@ -82,7 +82,7 @@ combined_compare (const void *void_first, const void *void_second)
 
 bool
 init_explode (RECODE_STEP step,
-	      RECODE_CONST_REQUEST request _GL_UNUSED_PARAMETER,
+	      RECODE_CONST_REQUEST request _GL_ATTRIBUTE_MAYBE_UNUSED,
 	      RECODE_CONST_OPTION_LIST before_options,
 	      RECODE_CONST_OPTION_LIST after_options)
 {
@@ -376,7 +376,7 @@ find_shifted_state (struct state *state, unsigned character,
 
 bool
 init_combine (RECODE_STEP step,
-	      RECODE_CONST_REQUEST request _GL_UNUSED_PARAMETER,
+	      RECODE_CONST_REQUEST request _GL_ATTRIBUTE_MAYBE_UNUSED,
 	      RECODE_CONST_OPTION_LIST before_options,
 	      RECODE_CONST_OPTION_LIST after_options)
 {
diff --git a/src/common.h b/src/common.h
index b40fa06..558bd2b 100644
--- a/src/common.h
+++ b/src/common.h
@@ -32,7 +32,6 @@
 #include "localcharset.h"
 #include "error.h"
 #include "gettext.h"
-#include "unused-parameter.h"
 
 #if ENABLE_NLS
 # define _(Text) gettext (Text)
diff --git a/src/dump.c b/src/dump.c
index 90f448d..8c0a7c1 100644
--- a/src/dump.c
+++ b/src/dump.c
@@ -436,6 +436,6 @@ module_dump (RECODE_OUTER outer)
 }
 
 void
-delmodule_dump (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_dump (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/ebcdic.c b/src/ebcdic.c
index a97ed31..683ebf6 100644
--- a/src/ebcdic.c
+++ b/src/ebcdic.c
@@ -139,7 +139,7 @@ static unsigned char const ascii_to_ebcdic_ibm[256] =
 
 static bool
 init_ascii_ebcdic (RECODE_STEP step,
-		   RECODE_CONST_REQUEST request _GL_UNUSED_PARAMETER,
+		   RECODE_CONST_REQUEST request _GL_ATTRIBUTE_MAYBE_UNUSED,
 		   RECODE_CONST_OPTION_LIST before_options,
 		   RECODE_CONST_OPTION_LIST after_options)
 {
@@ -174,7 +174,7 @@ init_ebcdic_ascii (RECODE_STEP step,
 
 static bool
 init_ascii_ebcdic_ccc (RECODE_STEP step,
-		       RECODE_CONST_REQUEST request _GL_UNUSED_PARAMETER,
+		       RECODE_CONST_REQUEST request _GL_ATTRIBUTE_MAYBE_UNUSED,
 		       RECODE_CONST_OPTION_LIST before_options,
 		       RECODE_CONST_OPTION_LIST after_options)
 {
@@ -210,7 +210,7 @@ init_ebcdic_ccc_ascii (RECODE_STEP step,
 
 static bool
 init_ascii_ebcdic_ibm (RECODE_STEP step,
-		       RECODE_CONST_REQUEST request _GL_UNUSED_PARAMETER,
+		       RECODE_CONST_REQUEST request _GL_ATTRIBUTE_MAYBE_UNUSED,
 		       RECODE_CONST_OPTION_LIST before_options,
 		       RECODE_CONST_OPTION_LIST after_options)
 {
@@ -268,6 +268,6 @@ module_ebcdic (RECODE_OUTER outer)
 }
 
 void
-delmodule_ebcdic (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_ebcdic (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/endline.c b/src/endline.c
index 575531f..e04d662 100644
--- a/src/endline.c
+++ b/src/endline.c
@@ -172,6 +172,6 @@ module_endline (RECODE_OUTER outer)
 }
 
 void
-delmodule_endline (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_endline (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/flat.c b/src/flat.c
index 57db166..3d24896 100644
--- a/src/flat.c
+++ b/src/flat.c
@@ -111,6 +111,6 @@ module_flat (RECODE_OUTER outer)
 }
 
 void
-delmodule_flat (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_flat (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/html.c b/src/html.c
index e564096..9faaade 100644
--- a/src/html.c
+++ b/src/html.c
@@ -929,6 +929,6 @@ module_html (RECODE_OUTER outer)
 }
 
 void
-delmodule_html (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_html (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/ibmpc.c b/src/ibmpc.c
index 5770969..3e4273d 100644
--- a/src/ibmpc.c
+++ b/src/ibmpc.c
@@ -387,6 +387,6 @@ module_ibmpc (RECODE_OUTER outer)
 }
 
 void
-delmodule_ibmpc (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_ibmpc (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/iconqnx.c b/src/iconqnx.c
index 9198936..58c9506 100644
--- a/src/iconqnx.c
+++ b/src/iconqnx.c
@@ -231,6 +231,6 @@ module_iconqnx (RECODE_OUTER outer)
 }
 
 void
-delmodule_iconqnx (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_iconqnx (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/iconv.c b/src/iconv.c
index 1eca011..cf60c87 100644
--- a/src/iconv.c
+++ b/src/iconv.c
@@ -241,6 +241,6 @@ module_iconv (RECODE_OUTER outer)
 }
 
 void
-delmodule_iconv (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_iconv (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/java.c b/src/java.c
index 360805f..7c63ce2 100644
--- a/src/java.c
+++ b/src/java.c
@@ -113,6 +113,6 @@ module_java (RECODE_OUTER outer)
 }
 
 void
-delmodule_java (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_java (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/lat1ansel.c b/src/lat1ansel.c
index d32f1c7..514d166 100644
--- a/src/lat1ansel.c
+++ b/src/lat1ansel.c
@@ -48,8 +48,8 @@ static struct translation diacritic_translations [] =
 static bool
 init_latin1_ansel (RECODE_STEP step,
 		   const struct recode_request *request,
-		   RECODE_CONST_OPTION_LIST before_options _GL_UNUSED_PARAMETER,
-		   RECODE_CONST_OPTION_LIST after_options _GL_UNUSED_PARAMETER)
+		   RECODE_CONST_OPTION_LIST before_options _GL_ATTRIBUTE_MAYBE_UNUSED,
+		   RECODE_CONST_OPTION_LIST after_options _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
   RECODE_OUTER outer = request->outer;
   
@@ -88,6 +88,6 @@ module_latin1_ansel (RECODE_OUTER outer)
 }
 
 void
-delmodule_latin1_ansel (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_latin1_ansel (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/lat1asci.c b/src/lat1asci.c
index d71f994..257595d 100644
--- a/src/lat1asci.c
+++ b/src/lat1asci.c
@@ -200,6 +200,6 @@ module_latin1_ascii (RECODE_OUTER outer)
 }
 
 void
-delmodule_latin1_ascii (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_latin1_ascii (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/lat1btex.c b/src/lat1btex.c
index 08584dd..5142f3a 100644
--- a/src/lat1btex.c
+++ b/src/lat1btex.c
@@ -179,6 +179,6 @@ module_latin1_bibtex (RECODE_OUTER outer)
 }
 
 void
-delmodule_latin1_bibtex (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_latin1_bibtex (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/lat1iso5426.c b/src/lat1iso5426.c
index 72c600e..ddec6ee 100644
--- a/src/lat1iso5426.c
+++ b/src/lat1iso5426.c
@@ -46,8 +46,8 @@ static struct translation diacritic_translations [] =
 static bool
 init_latin1_iso5426 (RECODE_STEP step,
                      const struct recode_request *request,
-                     RECODE_CONST_OPTION_LIST before_options _GL_UNUSED_PARAMETER,
-                     RECODE_CONST_OPTION_LIST after_options _GL_UNUSED_PARAMETER)
+                     RECODE_CONST_OPTION_LIST before_options _GL_ATTRIBUTE_MAYBE_UNUSED,
+                     RECODE_CONST_OPTION_LIST after_options _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
   RECODE_OUTER outer = request->outer;
 
@@ -86,6 +86,6 @@ module_latin1_iso5426 (RECODE_OUTER outer)
 }
 
 void
-delmodule_latin1_iso5426 (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_latin1_iso5426 (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/lat1ltex.c b/src/lat1ltex.c
index 294c28d..0eae33a 100644
--- a/src/lat1ltex.c
+++ b/src/lat1ltex.c
@@ -181,6 +181,6 @@ module_latin1_latex (RECODE_OUTER outer)
 }
 
 void
-delmodule_latin1_latex (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_latin1_latex (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/lat1txte.c b/src/lat1txte.c
index 938bf25..568a3dd 100644
--- a/src/lat1txte.c
+++ b/src/lat1txte.c
@@ -226,6 +226,6 @@ module_latin1_texte (RECODE_OUTER outer)
 }
 
 void
-delmodule_latin1_texte (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_latin1_texte (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/mule.c b/src/mule.c
index 4ea6774..66d2001 100644
--- a/src/mule.c
+++ b/src/mule.c
@@ -114,6 +114,6 @@ module_mule (RECODE_OUTER outer)
 }
 
 void
-delmodule_mule (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_mule (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/outer.c b/src/outer.c
index f76f0a4..e1d627f 100644
--- a/src/outer.c
+++ b/src/outer.c
@@ -27,7 +27,7 @@
 `-----------------------------------------------------------------------*/
 
 _GL_ATTRIBUTE_CONST bool
-reversibility (RECODE_SUBTASK subtask _GL_UNUSED_PARAMETER, unsigned code _GL_UNUSED_PARAMETER)
+reversibility (RECODE_SUBTASK subtask _GL_ATTRIBUTE_MAYBE_UNUSED, unsigned code _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
   return false;
 }
@@ -288,7 +288,7 @@ declare_strip_data (RECODE_OUTER outer, struct strip_data *data,
 `---------------------------------------------------------------*/
 
 static void
-estimate_single_cost (RECODE_OUTER outer _GL_UNUSED_PARAMETER, RECODE_SINGLE single)
+estimate_single_cost (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED, RECODE_SINGLE single)
 {
   int cost;
 
diff --git a/src/permut.c b/src/permut.c
index 4ae2a91..c2faa98 100644
--- a/src/permut.c
+++ b/src/permut.c
@@ -115,6 +115,6 @@ module_permutations (RECODE_OUTER outer)
 }
 
 void
-delmodule_permutations (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_permutations (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/quoted.c b/src/quoted.c
index 2ac2173..780fe78 100644
--- a/src/quoted.c
+++ b/src/quoted.c
@@ -362,6 +362,6 @@ module_quoted_printable (RECODE_OUTER outer)
 }
 
 void
-delmodule_quoted_printable (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_quoted_printable (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/recode.c b/src/recode.c
index 39399b8..bb51836 100644
--- a/src/recode.c
+++ b/src/recode.c
@@ -35,7 +35,7 @@ extern const char *program_name;
 #include <stdarg.h>
 
 _GL_ATTRIBUTE_FORMAT_PRINTF_SYSTEM (2, 3) void
-recode_error (RECODE_OUTER outer _GL_UNUSED_PARAMETER, const char *format, ...)
+recode_error (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED, const char *format, ...)
 {
   va_list args;
 
@@ -47,7 +47,7 @@ recode_error (RECODE_OUTER outer _GL_UNUSED_PARAMETER, const char *format, ...)
 }
 
 _GL_ATTRIBUTE_FORMAT_PRINTF_SYSTEM (2, 3) void
-recode_perror (RECODE_OUTER outer _GL_UNUSED_PARAMETER, const char *format, ...)
+recode_perror (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED, const char *format, ...)
 {
   int saved_errno = errno;
   va_list args;
diff --git a/src/rfc1345.c b/src/rfc1345.c
index df86fbc..1891b30 100644
--- a/src/rfc1345.c
+++ b/src/rfc1345.c
@@ -238,7 +238,7 @@ term_rfc1345 (RECODE_STEP step)
 static bool
 init_rfc1345 (RECODE_CONST_REQUEST request,
 	      RECODE_STEP step,
-	      RECODE_CONST_OPTION_LIST options _GL_UNUSED_PARAMETER)
+	      RECODE_CONST_OPTION_LIST options _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
   RECODE_OUTER outer = request->outer;
   struct local *local;
@@ -307,6 +307,6 @@ module_rfc1345 (RECODE_OUTER outer)
 }
 
 void
-delmodule_rfc1345 (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_rfc1345 (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/testdump.c b/src/testdump.c
index 9b52076..dd9d26d 100644
--- a/src/testdump.c
+++ b/src/testdump.c
@@ -387,6 +387,6 @@ module_testdump (RECODE_OUTER outer)
 }
 
 void
-delmodule_testdump (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_testdump (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/texinfo.c b/src/texinfo.c
index 3436e11..b4cba8a 100644
--- a/src/texinfo.c
+++ b/src/texinfo.c
@@ -86,6 +86,6 @@ module_texinfo (RECODE_OUTER outer)
 }
 
 void
-delmodule_texinfo (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_texinfo (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/ucs.c b/src/ucs.c
index b6081f8..a0e61dc 100644
--- a/src/ucs.c
+++ b/src/ucs.c
@@ -627,6 +627,6 @@ module_ucs (RECODE_OUTER outer)
 }
 
 void
-delmodule_ucs (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_ucs (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/utf16.c b/src/utf16.c
index c1b9ef6..b5deaea 100644
--- a/src/utf16.c
+++ b/src/utf16.c
@@ -213,6 +213,6 @@ module_utf16 (RECODE_OUTER outer)
 }
 
 void
-delmodule_utf16 (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_utf16 (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/utf7.c b/src/utf7.c
index cd4a9a5..849dc63 100644
--- a/src/utf7.c
+++ b/src/utf7.c
@@ -295,6 +295,6 @@ module_utf7 (RECODE_OUTER outer)
 }
 
 void
-delmodule_utf7 (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_utf7 (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/utf8.c b/src/utf8.c
index f41550e..56b60d1 100644
--- a/src/utf8.c
+++ b/src/utf8.c
@@ -247,6 +247,6 @@ module_utf8 (RECODE_OUTER outer)
 }
 
 void
-delmodule_utf8 (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_utf8 (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/varia.c b/src/varia.c
index f6f8c85..0521348 100644
--- a/src/varia.c
+++ b/src/varia.c
@@ -415,6 +415,6 @@ module_varia (RECODE_OUTER outer)
 }
 
 void
-delmodule_varia (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_varia (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }
diff --git a/src/vn.c b/src/vn.c
index 96ef6a7..d935810 100644
--- a/src/vn.c
+++ b/src/vn.c
@@ -457,6 +457,6 @@ module_vietnamese (RECODE_OUTER outer)
 }
 
 void
-delmodule_vietnamese (RECODE_OUTER outer _GL_UNUSED_PARAMETER)
+delmodule_vietnamese (RECODE_OUTER outer _GL_ATTRIBUTE_MAYBE_UNUSED)
 {
 }